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Comparative Study
. 2016 Aug;111(8):528-31.
doi: 10.1590/0074-02760160093.

Comparative growth of spotted fever group Rickettsia spp. strains in Vero cells

Arannadia Barbosa Silva  1   2 , Myrian Morato Duarte  3 , Vinicius Figueiredo Vizzoni  2   4 , Ana Íris de Lima Duré  3 , Diego Montenegro Lopéz  2   5 , Rita de Maria Seabra Nogueira  6 , Carlos Augusto Gomes Soares  4 , Erik Machado-Ferreira  4 , Gilberto Salles Gazêta  1   2
Affiliations
Comparative Study

Comparative growth of spotted fever group Rickettsia spp. strains in Vero cells

Arannadia Barbosa Silva et al. Mem Inst Oswaldo Cruz. 2016 Aug.

Abstract

In Brazil, the spotted fever group (SFG) Rickettsia rickettsii and Rickettsia parkeri related species are the etiological agents of spotted fever rickettsiosis. However, the SFG, Rickettsia rhipicephali, that infects humans, has never been reported. The study of growth dynamics can be useful for understanding the infective and invasive capacity of these pathogens. Here, the growth rates of the Brazilian isolates R. rickettsii str. Taiaçu, R. parkeri str. At#24, and R. rhipicephali HJ#5, were evaluated in Vero cells by quantitative polymerase chain reaction. R. rhipicephali showed different kinetic growth compared to R. rickettsii and R. parkeri.

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Figures

Fig. 1
Fig. 1. : visualization of Vero cells infected with spotted fever group Rickettsia spp. strains. (A) Photomicrographs illustrating the presence of Rickettsia spp. in Vero cells and uninfected Vero cells (Control) stained according to the Giménez method (Giménez 1964) (1000× magnification, optical microscope Olympus DP72) at 24, 48 and 72 h post bacterial inoculation; (B) percentage of Vero cells infected with R. rickettsii str. Taiaçu, R. parkeri str. AT#24, and R. rhipicephali str. H#J5 at the same time points. The results were statistically significant (Time course F3,18 = 223,56; p = 0.000; Species F2,18 = 5,10; p = 0.018; interaction, F6,18 = 4,43; p = 0,006; 95% CI; Levene’s = 0.07).
Fig. 2
Fig. 2. : relative quantification of spotted fever group Rickettsia spp. strains in Vero cells. (A) Relative growth curves of R. rickettsii str. Taiaçu, R. parkeri str. AT#24, and R. rhipicephali str. H#J5 in Vero cells at 1, 2, 24, 48 and 72 h post bacterial inoculation. There was a statistically significant difference between species [F4,65 = 304,90; p = 0.000; 95% confidence interval (CI)], an interaction between time and species (F8,65 = 114,50; p = 0.000; 95% CI). (B) Comparative ratio of R. rhipicephali abundance to those of R. rickettsii and R. parkeri, after infection. Comparisons with R. parkeri (white bars) and R. rickettsii (black bars) are presented. Rickettsia sp. abundances were determined as the relative amount of bacterial ompA / eukaryotic ß-actin at 2, 24, 48 and 72 h.
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